But the agencies inhabit a curious halfway-house world. For all the decentralisation of management, they remain part of the Civil Service, referring politically contentious matters to ministers. And some agency senior managers have taken a vow of public silence in the run-up to the general election, in case they say anything that could be used politically.
Sarah Tyacke, Keeper of the Public Records, is one of the more outgoing of agency chief executives. It could be argued that her job, looking after 900 years of government history and former secrets, is as politically sensitive as any, but only in the very long term. "There isn't anybody longer term than me," points out Mrs Tyacke.
Enthusiasm pours out of Mrs Tyacke, not only about the work of the Public Record Office, but also for the way its conversion to an executive agency five years ago has allowed her to be an effective manager. "The executive agency model was seen to be the best way to organise ourselves managerially, so that we got on board the new ideas that were coming in: management boards, some commercial element, making the management target-oriented, and actually delivering what we said we were going to deliver," recalls Mrs Tyacke.
"Although staff remain civil servants, we have been given more leeway to bring in new pay and grading structures to suit our own conditions, to alter hours of service. For example, from April we will be opening later in the evenings and will be launching a family history unit, using microfilm, in central London. We are much more flexible. We have a new e-mail distance inquiry system which we are just bringing on stream. We can do all that more easily perhaps than if we were a conventional department still.
"Prior to agency status there was no target setting, there was no corporate plan or business plan, neither was there a statement of the relationship between myself and the minister and the sponsoring department, the Lord Chancellor's Department. All that is now written down, rather than `in the ether' as it was in the traditional Civil Service."
Mrs Tyacke is responsible for 470 staff and a budget of pounds 30m. She is also the accounting officer for her service, and as such can be called to appear before the Public Accounts Committee of the House of Commons. "The Public Record Office has been more exposed in the last five years than it was before. It explains to the public what we can deliver, which has immensely improved the public service."
"It has made us think carefully about our [statutory] objectives, and has brought it home to us that we have to provide the best service for the resources we have got, and to seek resources from elsewhere to improve things."
User surveys have become a core element of service monitoring, and targets for improvement are based on what users say are the factors that are important to them. "This is not to say that the service wasn't good before, but as it wasn't monitored there was no means of knowing."
The Kew buildings - which since a year ago have housed all the main national public records - attract an annual 80,000 visitors who now benefit from the use of new technology. Improvements to record storage and retrieval have become imperative with the massive increase in state records during the 20th century. Three million badly damaged First World War service records are to be stored on microfilm thanks to a heritage lottery grant. Eventually, some records may be stored on computer disk after being scanned from paper.
Other developments are aimed at attracting private finance. One of these may be to work in partnership with a commercial business to run an e-mail service for family history searches, aimed at the United States. But such proposals can only go ahead if endorsed by ministers. Finding a compromise between commercial opportunities, management efficiency and the politically acceptable lies at the heart of executive agenciesn